Electromechanically actuated fluid switch

ABSTRACT

An electromechanically actuated fluid switch is disclosed in which the fluid output condition is tristable. The fluid output condition is selected by placing a voltage on a piezoelectric strip which, in turn, controls the position of the switching element. The three distinct fluid output conditions correspond to applied electrical signals of &#39;&#39;&#39;&#39;+,&#39;&#39;&#39;&#39; &#39;&#39;&#39;&#39;-&#39;&#39;&#39;&#39; and &#39;&#39;&#39;&#39;0.&#39;&#39;&#39;&#39; Since the switching function is not performed by the piezoelectric strip, but by a separate switching element, the configuration and surface finish of that element may be selected to provide desired fluid flow properties.

United States Patent 1191 1111 3,771,567 1451 Nov. 13,1973

Linden [54] ELECTROMECHANICALLY ACTUATED 3,457,933 7/1969 Craft 137/831 F U SWITCH 3,495,253 2/1970 Richards.... 137/822 3,605,780 9/1971 Kranz 137/610 Inventor: Richard Eugene Llnden, 3,628,568 12/1971 Green 137/610 Reynoldsburg, Ohio [73] Assignee: Bell Telephone Laboratories, Primary Examiner-Robert Nilson Incorporated, Murray Hill, Attorney-W. L. Keefauver et al.

[22] F1led: July 13, 1972 [57] ABSTRACT [2]] Appl' 271,382 An electromechanically actuated fluid switch is disclosed in which the fluid output condition is tristable. 52 US. Cl. ..'137/625.44, 137/597, 137/610, The fluid Output condition is selected y placing 37 22 37 3 voltage on a piezoelectric strip which, in turn, controls 51 1111.111. F156 3/08 the Position of the switching element The three 58 Field 61 Search 137/597, 610, 612, finer fluid Output conditions correspond to pp 37 2544 2 3 electrical signals of and 0. Since the switching function is not performed by the piezoelec- [56] References Cited tric strip, but by a separate switching element, the UNITED STATES PATENTS configuration and surface finish of that element may be selected to provide desired fluid flow properties. 3,187,762 6/1965 Norwood 137/831 3,556,119 1/1971 Ankeney 137/831 X 1 Claim, 5 Drawing Figures I T T f r J; I g 20 1a 4s 4l 35 Patented Nov. 13, 1973 2 Sheets-Sheet l Patented Nov. 13, 1973 3,771,567

2 Sheets$heet 2 FIG. 3

ELECTROMECHANICALLY ACTUATED FLUID SWITCH This invention relates to fluid switches and, more particularly, to electromechanically actuated fluid switches.

Background of the Invention Fluid switches are used to provide a variety of logic functions depending upon the arrangement of the inputs and outputs. Typical of such switches are U. S. Pats. No. 3,187,762, issued to R. E. Norwood on June 8, 1965, 3,457,933, issued to D. J. Craft on July 29, 1969, and 3,605,780, issued to W. Kranz on Sept. 20, 1971. These devices are actuated either electromagnetically or piezoelectrically. As a result, the switching element, which is movable to selectively direct the input to a desired output, must be either magnetically responsive or must be fabricated from piezoelectric material.

Unfortunately, magnetic material and piezoelectric material frequently have a textured surface which interferes with the smooth flow lines desired in the switched fluid. The configurations of such elements are also frequently dictated more by the operating characteristics of the material than by the fluid flow patterns being controlled. For example, a magnetically actuated element may require a large surface area to provide sufficient magnetic attractive force, while only a small area is required, or even desired, for switching the fluid.

As the area of these elements increases, fluid impedance or resistance is introduced, resulting in an increase in the unrecovered input power. Similarly, the introduction of a textured surface into the fluid flow region will cause increased fluid resistance and turbulence. Not only is power thereby lost, but spurious fluid flow paths may result, producing fluid noise and degrading the quality of the fluid signals. Configurations which might be very beneficial from a fluid flow point of view may be impossible or impractical to provide due to the mechanical limitations of these materials.

Molded plastic has been found to be an excellent material for fabricating fluid devices. The device configuration may be very intricate without unduly increasing device cost. Surface finishes may be readily controlled to produce very smooth surfaces in the areas where fluid impinges. Substantial improvement in the performance of fluid switches could be anticipated by replacing the conventional switching element with an element fabricated from molded plastic.

It is therefore an object of my invention to provide a fluid switch in which the configuration and surface finish of the switching element are dictated by the fluid flow characteristics desired and not by the requirement of the actuating mechanism.

Summary Of the Invention In an illustrative embodiment of my invention, two fluid inputs and two fluid outputs connect to a chamber in which a piezoelectric actuating strip is mounted. A movable switching element is also mounted in the chamber and positioned to move responsive to the action of the piezoelectric strip. The end of this chamber opposite the inputs is vented to the atmosphere. In its unoperated position, or that position in which the piezoelectric strip has no net voltage acting on it, the output from the device is through the vent to the atmosphere. Upon the application of a positive potential to the piezoelectric strip, the strip will bend, thereby moving the switching element and diverting the flow from one input to a selected output port. If a negative voltage is applied to the piezoelectric strip, the-switching element is moved to its third stable position and the flow from the other input is diverted to a second selected output.

Description of the Drawing path indicated for a first position of the switch element;

FIG. 4 shows the device of FIG. 1 with the fluid .flow path indicated for a second position of the switch element; and

FIG. 5 shows the device of FIG. 1 with the fluid flow path indicated for a third position of the switch element.

Description of the Illustrative Embodiment Fluid devices may be constructed from any rigid, nonporous material including glass, ceramic, plastic, and metal. Such devices generally comprise a base into which the desired passages are molded, impressed, or etched, and a cover which provides a fluid-tight seal when secured to the base by any of a number of methods such as adhesives, fasteners, clamps, or the like. For ease of illustration, the drawings of FIGS. 1 through 5 depict a device having a glass cover. This was done to permit the interior of the device to be shown without the confusing presence of cross-section lines. This should in no way be interpreted as a limitation on a material suitable for use in a device, since any rigid, nonporous material'is applicable.

The particular device 10 shown in FIGS. 1 and 2 comprises a first fluid input 14 and a second fluid input 15, which connect to independent fluid flow sources (not shown). These sources provide fluid flow selectively, depending on system conditions. the inputs l4 and 15 communicate respectively by nozzles 34 and 35 with a cavity area 11. The nozzles act to generate a fluid jet when fluid pressure is present at the respective inlet.

Positioned to substantially bisect cavity 11 is a piezoelectric strip 20. Strip 20 may be deflected from its null position either in a positive direction (upward) or a negative direction (downward), depending upon the voltage potential applied to it (through means not shown, but which are well known in the art). The inlet, or upstream, end of strip 20 is firmly held in the body of device 10. The downstream end 21 of strip 20 is cantilevered and free to move when the strip deflects in response to an applied voltage.

Positioned astride free end 21 is a flow diverter 23 comprising two diverter legs 24 and 25. Legs 24 and 25 have rounded bearing surfaces 28 and 29, respectively, which contact free end 21 and move in response to the movement of strip 20. Legs 24 and 25 are hinged at hinges 26 and 27, respectively, and are connected to each other by brace 37 so that they move together in response to any movement of strip 20.

At the downstream end of cavity 11 are two fluid receivers 44 and 45. Fluid receivers 44 and 45 connect respectively to fluid outputs 17 and 18 which, in turn, connect to additional parts of the system in which the output signals are used. These have not been shown, although they would be well known to one skilled in the art. Also, at the downstream end of cavity 11 is a vent passage 19 which connects to the ambient atmosphere.

Along the periphery of legs 24 and 25 is a high ridge, or rib, 40 and 41, respectively. Ribs 40 and 41 define a passageway between nozzles 34 and 35 and the respective receivers 44 and 45.

The operation of device 10 can be best understood by referring to FIGS. 3 through which show the device in various operable states. In FIG. 3, device is shown in position with no voltage applied to strip 20. This will be referred to as the 0 position. In this position nozzles 34 and 35 are isolated from receivers 44 and 45 by ribs 40 and 41, respectively. Flow issuing from nozzles 34 and 35 is directed by ribs 40 and 41 through cavity area 11 to exit device 10 via vent 19.

If a positive potential is applied to strip 20, it will take the configuration shown in FIG. 4. The movement of strip 20 will re-position flow diverter 23. In this position, the fluid jet issuing from nozzle 34 is still isolated from receiver 44 by rib 40. Therefore, the jet issuing from nozzle 34 is directed through chamber area 11 to exit device 10 via vent 19. However, rib 41 is now positioned on the opposite side of nozzle 35 from the position it occupied in FIG. 3 when no potential was applied to strip 20. In the new position, the fluid jet issuing from nozzle 35 is diverted by rib 41 to be received at fluid receiver 45 which connects to fluid output 18. Thus, in this position, which will be referred to as the position, fluid flow originating at fluid input 14 exits the device via vent 19 while flow originating at fluid input exits the device via fluid output 18.

The application of a negative potential to strip is shown in FIG. 5. Due to this applied voltage, strip 20 moves in the direction shown. This causes flow diverter 23 to also move as shown within chamber area 11. In this position, rib 41 once again isolates fluid receiver 45 from nozzle 35. As a result, the fluid jet issuing from nozzle 35 passes through chamber area 1 1 and exits device 10 via vent 19.

Rib 40 is now positioned on the opposite side of nozzle 34. The fluid jet issuing from nozzle 34 is now isolated from chamber area 11 by rib 40 which diverts the issued jet to be received at receiver 44. Thus, in this position, which will be called the position, fluid flow originating at fluid input 14 is received at fluid receiver 44 and exits device 10 via fluid output 17. Flow originating at fluid input 15 passes through the device 10 and exits via vent 19.

It will be apparent that the device just described is nonlatching. That is,-if either the potential or the potential is removed from strip 20, it will return to the 0 position as shown in FIG. 3. It should be equally clear that this is not a limitation of the device and is not a requirement, since by properly positioning of hinges 26 and 27, a device could be made latching. That is to say, a device could be so arranged that, upon application of a potential, flow diverter 23 would remain in the position until a potential were applied. At that point, flow diverter 23 would switch to the position and remain there until a potential is applied to the device. Thus, a latching device could be made bistable as opposed to the embodiment described above, which is tristable. Application of a negative potential less than the potential would return strip 20 to the 0 position without causing the strip to move all the way to the position. Thus, it can be seen that if tristable operation is desired, this can also be achieved with a latching device.

Referring again to FIG. 2, it can be seen that the embodiment described includes a top plate 30, an active layer 31 and a bottom plate 32. Active layer 31 has been shown as a single piece of molded plastic into which strip 20 may be positioned. It should, of course, be apparent that this specific embodiment is not the only available arrangement. For example, plate 30 and layer 31 could readily be made in a single molded piece with flow diverter 23 being a separately molded item which is then positioned in cavity area 11 when strip 20 is assembled into the device. Although flow diverter 23, hinges 26 and 27, and the remainder of the active layer 31 are shown as being molded from a single piece, this is not a requirement since flow diverter 23 could readily be made as a separate item and assembled into layer 31.

Although inputs 14 and 15 have been described as being connected to independent fluid flow sources, it should be apparent that a single common fluid flow source could also be connected to both inputs. It should be equally apparent that outputs 17 and 18 could also connect to a single common output. With independent inputs and a common output, device 10 would function as an OR logic gate. With independent outputs and either independent or common inputs, device 10 functions as a transducer.

Although it is not necessary that device 10, or, for that matter, even active layer 31, be fabricated by molding or even fabricated from plastic material, it should be apparent that this is a signal advantage of this arrangement. The advantage being that material comprising flow diverter 23, and, in particular, ribs 40 and 41, and the edge surfaces of chamber area 11 may be selected solely on the basis of the surface finish and its effect upon fluid resistance and the flow patterns established in moving through device 10. Since the surface of an active element, such as strip 20, is not involved in the movement of fluid through the device, the localized turbulence and fluid resistance created by the irregularities and surface imperfections of such materials will not have an effect on the active signals of the device.

What is claimed is:

l. A fluid switch comprising a first nozzle for generating a first fluid jet;

a second nozzle for generating a second fluid jet;

a switching chamber forming a cavity into which the generated jets flow;

a first fluid receiver communicating with the switching chamber to receive the first jet;

a second fluid receiver communicating with the switching chamber to receive the second jet;

a vent connected to the switching chamber through which fluid exits the switch;

a flow diverter located within the switching chamber and selectively movable to three positions, in a first position the diverter isolates the first and second receivers from the generated jets and diverts the jets to exit the switch via the vent, in a second position the diverter isolates the first receiver from the lectively control the positioning of the flow diverter, said means moving the diverter to the first position when a first signal is present, to the second position when a second electrical signal is applied, and to the third position when a third electrical signal is present. 

1. A fluid switch comprising a first nozzle for generating a first fluid jet; a second nozzle for generating a second fluid jet; a switching chamber forming a cavity into which the generated jets flow; a first fluid receiver communicating with the switching chamber to receive the first jet; a second fluid receiver communicating with the switching chamber to receive the second jet; a vent connected to the switching chamber through which fluid exits the switch; a flow diverter located within the switching chamber and selectively movable to three positions, in a first position the diverter isolates the first and second receivers from the generated jets and diverts the jets to exit the switch via the vent, in a second position the diverter isolates the first receiver from the first jet and diverts the first jet to exit the switch via the vent while simultaneously directing the second jet to the second receiver, and in a third position the diverter isolates the second receiver from the second jet and directs the second jet to exit the switch via the vent while simultaneously directing the first jet to the first receiver; and means responsive to applied electrical signals to selectively control the positioning of the flow diverter, said means moving the diverter to the first position when a first signal is present, to the second position when a second electrical signal is applied, and to the third position when a third electrical signal is present. 